1. Field of the Invention
This invention relates to vacuum packaging methods and apparatus. More particularly, this invention relates to the production of integral package pairs in which different products are simultaneously packaged in adjoining packages to provide different atmospheric conditioning for the products during the package formation.
2. Description of the Prior Art
Evacuated packages formed of heat-sealable flexible packaging materials with a low rate of gas permeability have found wide acceptance because of their extended shelf life as compared to conventional packages. Where atmospheric pressure surrounding a vacuum package could cause mechanical damage to the packaged product or to its container, inert gases such as nitrogen may be introduced into the package after evacuation to reduce or eliminate the pressure differential to which the package walls would otherwise be subjected. In producing such packages automatically the packages may be partially sealed before the evacuating or gassing operations are performed.
The packages are often formed from two continuous sheets of packaging material. One sheet may be formed into cup-shaped containers, and the other sheet laid down as a cover or top over the containers. An aperture may be formed adjacent the container for evacuation and possible subsequent back-filling with gas. A web-lifter may be provided in the machine sealing station which tents the top web to improve the evacuation and/or gassing of the packages. The aperture opening may be located between two adjacent containers which can be processed in the same manner because of the common opening. More detail is available in U.S. Pat. No. 3,061,984 to R. A. Mahaffy which is assigned to the Assignee of the present invention.